JP5880026B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that develops a latent image formed on an image carrier such as a photosensitive drum with a developer, and an image forming apparatus including the developing device.

An image forming apparatus such as a copying machine includes a developing unit in which a two-component developer including, for example, a carrier and toner is accommodated, and develops a latent image formed on a photosensitive drum with the developer.
As an example of the development system, the developer contained in the developing unit is circulated and conveyed, and a replenishment developer is replenished little by little from the replenishment port, and a part of the developer that has become excessive due to the replenishment is removed. There is a so-called trickle development system that discharges to the outside from the discharge port.

In this trickle development method, the carrier contained in the developer is gradually changed from the old one to the new one, so that the deteriorated carrier hardly remains and it is possible to suppress the deterioration of the developer and realize high image quality. it can.
The trickle development unit is optimized so that the developer discharge amount is constant when installed in a regular horizontal position, but the development unit is not always installed in a horizontal position. .

For example, when the image forming apparatus is installed in a tilted posture where the discharge port of the developing unit is positioned below instead of in a horizontal posture, or when the horizontal posture and the tilted posture are alternately repeated in the ship due to shaking caused by ocean waves and so on.
When the developing section is inclined, the amount of developer discharged per unit time is larger than when the developing section is in a horizontal position, and the amount of developer in the developing section is likely to decrease sharply. When the developer rapidly decreases, the developer The development performance such as developing fading is deteriorated due to the occurrence of local conveyance unevenness.

  Therefore, Patent Document 1 discloses a circulation path for circulating and transporting the developer, and after branching from the circulation path, again joining the circulation path and transporting a part of the developer flowing in from the branch position. In a configuration that includes a branch path and discharges the developer from a discharge port provided in the middle of the branch path, when detecting that the developing unit is installed in an inclined posture, the discharge port provided in the branch path is shielded by a shutter. The structure to perform is disclosed.

  Since the discharge port is shielded when the developing unit is in the inclined posture, it is possible to prevent a large amount of developer from being discharged from the discharge port in the inclined posture as compared with a configuration in which the developing unit is not shielded.

JP 2010-217501 A

However, in the configuration of Patent Document 1, when the branch path is positioned below the horizontal posture due to the inclined posture of the developing unit, the development that should originally exist in the circulation path if the horizontal posture is caused by gravity. Most of the agent enters the branching path, and the developer is present in a state where the density is much higher than that in the horizontal posture in the branching path.
In this state, when the developing unit is changed from the inclined position to the horizontal position and the discharge port is opened, many developers that are present in the branching path and are supposed to exist in the circulation path. However, there is a problem that the entire amount of the developer in the developing section is rapidly reduced.

  The present invention has been made in view of the above problems, and in a method of discharging an excess developer while replenishing the developer for replenishment, the developer is discharged due to the inclination of the developing device. An object of the present invention is to provide a developing device and an image forming apparatus provided with the developing device that can suppress the increase in the amount of developer in the developing device.

In order to achieve the above object, a developing device according to the present invention circulates and conveys a developer accommodated in a housing, and replenishes a replenishment developer into the housing, while supplying an excess amount of the developer. The developer is discharged from the discharge port to the outside. The developer being conveyed is supplied to the developer carrier, and is formed on the image carrier of the image forming apparatus by the developer carried on the developer carrier. A developing device for developing the latent image, a circulation path for circulating and conveying the developer, and a part of the developer branched from the circulation path and flowing into the discharge path toward the discharge port And a damming means for damming the developer that flows through the branch path toward the discharge port at a position between the branch path inlet and the discharge port, and the development existing in the branch path A rotary conveying member that conveys the agent along the rotation axis direction; Wherein the damming means is a dam provided in a position between from the entrance of the branch passage down to the outlet, the developer until the developer surface of the developer exceeds the dam The developer is stored on the upstream side in the developer conveyance direction of the dam, and when the dam is crossed, the developer exceeding the dam is discharged from the discharge port, and the branch path is formed of a cylindrical member, and the rotation The conveying member is disposed in the inner space of the cylindrical member so that the axial direction thereof is along the developer conveying direction, the discharge port is provided in the cylindrical member, and the dam is connected to the rotary conveying member A circular rotating portion that is provided over the circumference of the rotation direction and rotates together with the rotary conveying member; and the circular rotating portion that extends along the circumferential direction on the inner surface of the cylindrical member and rotates. The rotation portion of the rotating portion including at least the lowest portion in the circumferential direction Characterized in that it comprises an arcuate stationary portion in sliding contact with the an outer peripheral surface of the.

Here, the circumferential length of the region of the fixed portion that is in sliding contact with the outer peripheral surface of the rotating portion may be less than the one turn and 40% or more of the one turn.
Here, the circumferential length may be less than 50% of the circumference, and both ends in the circumferential direction of the fixing portion may be located below a horizontal plane passing through the axis of the conveying screw .

Here, the switching unit includes an opening / closing member that performs blocking and releasing of the developer by switching between blocking and opening of the developer flow path, and the control unit detects an inclination posture of the own device. Then, the flow path of the developer may be switched from opening to blocking by the opening / closing member.
Here, the opening / closing member is a shutter that is movable between a first position that blocks the flow path of the developer and a second position that opens the flow path of the developer, and the control means includes: The switching from opening to blocking of the flow path may be performed by moving the shutter from the second position to the first position.

Et al is, the branch passage, after branched from the circulation path, again, a flow path merging into the circulation path may be the discharge port in the middle of the flow path is provided.

  According to the above configuration, even when the developing device is inclined, the developer that tries to flow from the circulation path toward the discharge port is blocked in the middle of the development apparatus. When a large amount of developer that should be present in an inclined position is prevented from flowing into the branch path, it is possible to prevent the total amount of developer contained in the developing device from rapidly decreasing than before. can do.

1 is a schematic diagram illustrating an overall configuration of a copier according to a first embodiment. 1 is a perspective view showing an entire developing unit provided in a copier. FIG. 3 is a cross-sectional view taken along the line AA shown in FIG. (A) is a top view which extracts and shows the apparatus front side part of a image development part, (b) is arrow sectional drawing in the BB line shown in FIG. FIG. 4 is an exploded perspective view illustrating a configuration of a developer damming unit provided in the developing unit. (A) is an external appearance perspective view which shows a mode that the opening part is open | released by the shutter of a developer damming part, (b) is sectional drawing in CC line shown to (a). (A) is an external appearance perspective view which shows a mode that the opening part is obstruct | occluded with the shutter of a developer damming part, (b) is sectional drawing in the DD line | wire shown to (a). FIG. 2 is a block diagram illustrating a configuration of a control unit provided in a copying machine. It is a flowchart which shows the processing content of the opening / closing control with respect to a image development part. FIG. 10 is a plan view showing a portion of the developing unit according to Embodiment 2 on the front side of the apparatus. It is sectional drawing when the part of the image development apparatus front side is cut | disconnected by the horizontal surface. It is a perspective view when a supply screw is seen from the direction of arrow F shown in FIG. It is a perspective view which shows the state which removed the supply screw shown in FIG. It is an expansion perspective view which shows the structure of the dam provided in a image development part. It is arrow sectional drawing of the dam in the GG line shown in FIG. It is a schematic diagram which shows a mode that the surface of a developer overflows over a dam. (A) is a figure which shows the experimental example of a mode that the fluctuation | variation range of the whole amount of a developer by the inclination of the image development part in an Example changes, (b) has shown the thing of the comparative example. It is a perspective view which shows the modification of a structure of a dam.

<Embodiment 1>
(1) Overall Configuration Embodiments of a developing device and an image forming apparatus according to the present invention will be described below using a tandem color copying machine (hereinafter simply referred to as “copying machine”) as an example.
FIG. 1 is a diagram showing an overall configuration of a copying machine 10 according to the present embodiment.

As shown in the figure, the copying machine 10 includes an image reading unit 11, an image forming unit 12, a feeding unit 13, a fixing unit 14, a control unit 15, and the like, and includes yellow (Y) and magenta (M ), Cyan (C) and black (K) colors are formed and reproduced on paper. Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, respectively.
The image reading unit 11 reads an image of a set original and outputs image data obtained by the reading.

The image forming unit 12 includes image forming units 20Y to 20K corresponding to Y to K colors, an intermediate transfer belt 21, and hoppers 7Y to 7K.
The image forming units 20Y to 20K include photosensitive drums 1Y to 1K, charging rollers 2Y to 2K disposed around the photosensitive drums 1Y to 1K, exposure units 3Y to 3K, developing units 4Y to 4K, primary transfer rollers 5Y to 5K, and photosensitive drums. Cleaners 6Y to 6K for cleaning 1Y to 1K are provided, and Y to K color toner images are formed on the photosensitive drums 1Y to 1K.

The developing units 4Y to 4K contain a two-component developer (hereinafter abbreviated as “developer”) including a carrier and a toner, and here, a trickle developing method is adopted as a developing method.
The intermediate transfer belt 21 is an endless belt, is stretched around a driving roller 22 and a driven roller 23, and is circulated and driven in a direction indicated by an arrow in FIG.
The hopper 7Y is detachable from a cartridge 9Y in which a Y-color replenishment developer is accommodated, and the Y-color replenishment developer in the mounted cartridge 9Y is supplied to the development unit 4Y by an instruction from the control unit 15. Supply. The same applies to the other hoppers 7M to 7K, and the cartridges 9M to 9K in which M to K replenishment developers are accommodated are detachable, and the replenishment developers in the mounted cartridges are controlled. According to an instruction from the unit 15, the toner is supplied to the developing units 4M to 4M.

The feeding unit 13 includes a paper feed cassette 31 that stores the paper S, a feed roller 32 that feeds the paper S in the paper feed cassette 31 one by one onto the transport path 37, and a transport roller that transports the fed paper S. A pair 33, a timing roller pair 34 for taking a timing to send the conveyed paper S to the secondary transfer position 351, a secondary transfer roller 35, and the like are provided.
The fixing unit 14 includes a fixing roller and a pressure roller that are pressed against each other, a heater for heating the fixing roller, and the like.

When the control unit 15 receives an execution instruction for copying or the like from a user via an operation panel (not shown), the control unit 15 controls the image reading unit 11 and the image forming unit 12 based on the instruction to start a copying operation.
Specifically, the image reading unit 11 is caused to read a document image, and the laser diodes of the exposure units 3Y to 3K are driven based on the image data obtained by reading. As a result, the laser light L for each color is emitted from the laser diodes of the exposure units 3Y to 3K, and the photosensitive drums 1Y to 1K are exposed and scanned line by line.

Before this exposure scanning, the photosensitive drums 1Y to 1K are uniformly charged by the charging rollers 2Y to 2K, and electrostatic latent images are formed on the photosensitive drums 1Y to 1K by the exposure scanning of the laser beam L. Is done. The formed electrostatic latent images are developed (development) with the developer stored in the developing units 4Y to 4K, and toner images are formed on the photosensitive drums 1Y to 1K.
The toner images of the respective colors are primary-transferred sequentially onto the intermediate transfer belt 21 by electrostatic force acting between the primary transfer rollers 5Y to 5K and the photosensitive drums 1Y to 1K. At this time, the image forming operations for the respective colors are executed at different timings so that the toner images are superimposed and transferred at the same position on the intermediate transfer belt 21. The color toner images superimposed on the intermediate transfer belt 21 are moved to the secondary transfer position 351 by the circulation drive of the intermediate transfer belt 21.

  In synchronization with the timing of the image forming operation, the sheet S is fed from the feeding unit 13 via the timing roller pair 34, and the sheet S is connected to the intermediate transfer belt 21 that is circulated and driven. It is sandwiched between the next transfer rollers 35 and conveyed. At that time, the toner images on the intermediate transfer belt 21 are secondarily transferred onto the sheet S all at once by the electrostatic force acting between the secondary transfer roller 35 and the driving roller 22.

The paper S that has passed the secondary transfer position 351 is conveyed to the fixing unit 14, and when passing through the fixing unit 14, the toner image on the paper S is heated and pressurized and fixed on the paper S, and then discharged. The paper is discharged through the roller pair 36 and stored in the storage tray 38.
(2) Configuration of Developing Unit FIG. 2 is a perspective view showing the entire developing unit 4Y, FIG. 3 is a cross-sectional view taken along the line AA shown in FIG. 2, and FIG. FIG. 4 is a plan view showing a front portion (front portion) 505 extracted from the developing unit 4Y, and FIG. 4B is a cross-sectional view taken along the line BB in FIG.

  As shown in FIG. 2, the developing unit 4Y is elongated along the X-axis direction (corresponding to the axial direction of the photosensitive drum 1Y) from the front side to the back side of the apparatus. The end on the lower left is called the front side of the apparatus, the end on the upper right is called the rear side of the apparatus, the vertical direction is called the Z-axis direction, and the direction perpendicular to both the X-axis and the Z-axis is called the Y-axis direction. The developing units 4Y to 4K are different in the color of the developer used, but basically have the same configuration. Therefore, the developing unit 4Y will be described below, and the developing units for other colors will be described as follows. Description is omitted.

As shown in FIGS. 2 to 4, the developing unit 4 </ b> Y includes a housing 50, a developing roller 51, a supply screw 52, a stirring screw 53, a discharge screw 54, a developer damming unit 55, and a concentration detection sensor 56. And a developing unit inclination detection sensor 57 and the like.
The housing 50 to the discharge screw 54 are elongated along the X-axis direction.
The housing 50 accommodates the developer D. The supply chamber 61, the stirring chamber 62, and the discharge chamber 63 are each formed in a cylindrical shape, and the stirring chamber 62 and the supply chamber are formed as shown in FIG. 4B. The chamber 61 and the discharge chamber 63 are arranged in this order along the Y-axis direction.

The stirring chamber 62 extends from the end portion on the front side of the apparatus to the end portion on the rear side of the apparatus along the X-axis direction, and the discharge chamber 63 extends only along the X-axis direction to the front portion 505. The supply chamber 61 is extended along the X-axis direction in the remaining portion except the front portion 505.
Although the supply chamber 61 and the stirring chamber 62 are partitioned by a partition wall 69, they communicate with each other through an opening 71 provided on the front side of the apparatus with the partition wall 69 interposed therebetween in the X-axis direction, and are provided on the rear side of the apparatus. It is configured to communicate through the opening 72.

Further, the end of the supply chamber 61 on the front side of the apparatus and the end of the discharge chamber 63 on the rear side of the apparatus communicate with each other through the opening 73, and the end of the discharge chamber 63 on the front side of the apparatus and the front side of the stirring chamber 62. This end portion communicates with each other through the opening 74.
In the Z-axis (up and down) direction, as viewed from the discharge chamber 63, there is a relationship in which the supply chamber 61 is located obliquely upward and the stirring chamber 62 is obliquely downward (FIG. 6B).

The developing roller 51 and the supply screw 52 are provided in the supply chamber 61, the stirring screw 53 is provided in the stirring chamber 62, and the discharge screw 54 is provided in the discharge chamber 63.
As shown in FIG. 3, the developing roller 51 is disposed in an opening provided in the supply chamber 61 at a position facing the photosensitive drum 1 </ b> Y, and has a cylindrical developing sleeve 511 and a developing sleeve 511. A magnet roller 512 inserted along the axial direction is provided.

The magnet roller 512 is provided such that portions where a plurality of magnetic poles, for example, N poles and S poles are alternately arranged in the circumferential direction, are arranged in order in the circumferential direction. It is fixed. Each of the magnetic poles extends along the axial direction.
The developing sleeve 511 is exposed to a portion facing the photosensitive drum 1Y through the opening of the housing 50 and is held by the housing 50 so as to be rotatable in a direction indicated by an arrow in FIG. The magnet roller 512 rotates while holding (carrying) the developer D on the surface by the magnetic force of the magnet roller 512.

The supply screw 52 is provided with spiral blades along the axial direction on the outer peripheral surface of the rotation shaft, and is arranged at a position facing the photoconductive drum 1Y with the developing roller 51 in the supply chamber 61, in the X direction. The housing 50 is rotatably supported in a parallel posture.
The supply screw 52 supplies the developer D in the supply chamber 61 to the developing roller 51 while conveying the developer D in the supply chamber 61 from the rear side of the apparatus toward the front side of the apparatus.

Each of the stirring screw 53 and the discharge screw 54 is provided with a spiral blade on the outer peripheral surface of the rotation shaft thereof, and is rotatably supported by the housing 50 in a posture parallel to the supply screw 52.
The agitating screw 53 conveys the developer D in the agitating chamber 62 from the front side of the apparatus to the rear side of the apparatus while agitating the developer D in the agitating chamber 62, and the discharging screw 54 conveys the developer D in the discharging chamber 63 by the rotation. Is conveyed from the rear side of the apparatus toward the front side of the apparatus.

The discharge screw 54 is provided with a reverse winding portion 541 (FIG. 4) having a reverse winding blade in which the turning direction of the spiral blade is opposite to that of the other portion only at the end portion on the rear side of the apparatus. .
The supply screw 52 receives the driving force of the developing roller 51 that is rotated by the driving force from a driving motor (not shown), and rotates in the direction indicated by the arrow in FIG. 3, and the stirring screw 53 passes through the supplying screw 52. In response to the driving force 51, it rotates in the direction indicated by the arrow in FIG.

  The discharge screw 54 rotates in the same direction as the stirring screw 53 by the driving force from the stirring screw 53. In the present embodiment, a pulley 91 is attached to the end of the stirring screw 53 on the front side of the apparatus protruding outside the housing 50, and a pulley 92 is attached to the end of the discharging screw 54 on the front side of the apparatus protruding outside the housing 50. Is attached to the pulleys 91 and 92, and the rotational driving force of the stirring screw 53 is transmitted to the discharge screw 54 via the belt 93.

A replenishment port 40 (FIG. 4A) for receiving the replenishment developer from the cartridge 9Y into the agitation chamber 62 is provided at the front portion of the agitation chamber 62, and the replenishment development from the cartridge 9Y. The agent is supplied to the developing unit 4Y through the cylindrical supply pipe 41.
The developer damming unit 55 opens and closes an opening 73 interposed between the end of the supply chamber 61 on the front side of the apparatus and the end of the discharge chamber 63 on the rear side of the apparatus by the shutter 81, and the developing unit 4Y. In the normal posture (horizontal posture), the opening 73 is opened, and the opening 73 is closed when the front side of the apparatus is inclined downward (the rear side of the apparatus is upward) with respect to the normal posture. . This opening / closing operation is controlled by the control unit 15. Details of the configuration of the developer damming portion 55 and the opening / closing control will be described later.

  The density detection sensor 56 is a sensor that is disposed at the bottom of the agitating chamber 62 and measures the ratio of the carrier and toner of the developer D conveyed through the agitating chamber 62, and a detection signal indicating the ratio of the carrier and toner is controlled by the control unit. Send to 15. The control unit 15 controls the hopper 7Y so that the ratio of the carrier and the toner falls within an appropriate range, and supplies the Y-color supply developer in the cartridge 9Y to the developing unit 4Y.

  The developing unit inclination detection sensor 57 includes, for example, a level, detects whether the developing unit 4Y is in a horizontal posture or an inclined posture, and sends the detection result to the control unit 15. The control unit 15 switches between opening and closing of the opening 73 by the shutter 81 of the developer damming unit 55 depending on whether it is in a horizontal posture or an inclined posture. Note that it is only necessary to detect the inclination of the developing unit 4Y with respect to the horizontal posture, and other detection means such as an angle sensor may be used.

  In such a configuration, when the developing roller 51, the supply screw 52, the stirring screw 53, and the discharge screw 54 are simultaneously rotated, the developer D in the supply chamber 61 is conveyed by the supply screw 52 from the rear side of the apparatus toward the front side of the apparatus. If the opening 73 is opened by the shutter 81 of the developer damming portion 55, a part of the developer D transported in the supply chamber 61 from the rear side of the apparatus to the front side of the apparatus is opened on the front side of the apparatus. The remaining portion is conveyed through the opening 73 to the discharge chamber 63 through the stirring chamber 62.

A reverse winding portion 541 provided at the end of the discharge screw 54 disposed in the discharge chamber 63 on the rear side of the apparatus is directed from the front side of the apparatus to the rear side with respect to the developer D (open from the discharge chamber 63 to the rear side). The transfer force is applied to the supply chamber 61 via the portion 73.
The conveying force of the reverse winding portion 541 is slightly weaker than the conveying force applied to the developer D by the supply screw 52, and the developer D is directed from the supply chamber 61 to the discharge chamber 63 through the opening 73. Only the difference between the conveyance force by the supply screw 52 and the reverse conveyance force by the reverse winding portion 541 of the discharge screw 54 is applied.

Therefore, in practice, only a part of the developer D conveyed to the front side of the apparatus by the supply screw 52 passes through the reverse winding portion 541 from the opening 73 and is conveyed into the discharge chamber 63, and most of the developer D is conveyed. It is conveyed to the stirring chamber 62 through the opening 71.
The developer D transported to the stirring chamber 62 is transported from the front side of the apparatus to the rear side of the apparatus by the stirring screw 53 and, when reaching the opening 72 on the rear side of the apparatus, is transported to the supply chamber 61 through the opening 72. Done (returned). Thereby, the circulation path 101 through which the developer D circulates and transports in the order of the supply chamber 61, the opening 71, the stirring chamber 62, and the opening 72 is formed.

  On the other hand, the developer D transported to the discharge chamber 63 is transported from the rear side of the apparatus to the front side of the apparatus by the discharge screw 54, and in the middle of the developer D, the developer D is discharged from the discharge port 59 provided on the bottom surface 502 of the discharge chamber 63. The part is discharged to the outside, and the remainder that has not been discharged is conveyed to the opening 74 on the front side of the apparatus. The developer D discharged from the discharge port 59 is stored in a tank (not shown).

The developer D transported to the opening 74 is transported through the opening 74 to the end of the stirring chamber 62 on the front side of the apparatus, and is then transported in the stirring chamber 62 toward the rear side of the apparatus by the stirring screw 53. At the opening 71, the developer merged from the supply chamber 61 through the opening 71 into the stirring chamber 62 is merged and further conveyed toward the rear side of the apparatus.
Thereby, after branching from the flow path for conveying a part of the developer D, that is, returning from the supply chamber 61 to the stirring chamber 62 through the opening 73, the discharge chamber 63, and the opening 74, that is, from the circulation path 101, A branch path 102 that joins the circulation path 101 is formed.

The total amount of the developer D accommodated in the housing 50 is increased by supplying a constant amount of the replenishment developer from the toner hopper 7Y by the trickle developing method. By being discharged from 59 to the outside, it is increased or decreased (fluctuated) within a certain range within the allowable range of the developer amount.
If the total amount of the developer D is too small, the amount of developer carried on the developing roller 51 is less than the minimum amount necessary for development, and the toner image on the photosensitive drum 1Y due to the development is faint. Cause development fading.

On the contrary, if the total amount of the developer D is too large, the rotational load of each screw such as the supply screw 52 is increased, the rotational torque is increased, and a large load is applied to the drive source such as the drive motor, causing the rotation failure of each screw. This may lead to failure of the drive source.
For this reason, the overall amount of the developer D is increased or decreased within a certain range within an allowable range suitable for each apparatus, in which development fading does not occur and rotation failure of each screw or failure of the drive source does not occur. The supply amount of the replenishment developer, the developer conveyance force by each screw such as the supply screw 52, and the like are determined in advance.

  The variation range of the total amount of the developer D may be within the allowable range of the developer amount. However, when the developing unit 4Y changes from the horizontal posture to the inclined posture, the opening 73 is left open. In other words, most of the developer D that should originally exist in the supply chamber 61 flows by gravity into the discharge chamber 63 through the opening 73 positioned below the supply chamber 61, and passes through the discharge chamber 63. As a result, it is discharged from the discharge port 59 to the outside. In this case, the total amount of the developer D is suddenly reduced from the original amount before the inclined posture, and the developer amount is not within the allowable range.

A certain amount of gap is provided between the spiral blade of the discharge screw 54 and the inner peripheral surface of the discharge chamber 63 in order to smoothly rotate the discharge screw 54. Even if it is inclined by about 3 °, a lot of developer D easily flows into the discharge chamber 63 through the gap between the bottom surface 502 of the discharge chamber 63 and the spiral blade of the discharge screw 54.
Therefore, in this embodiment, when it is detected that the developing unit 4Y has changed from the horizontal posture to the inclined posture, the opening portion 73 is switched from the open state to the closed state by the shutter 81 of the developer damming unit 55. The developer D is prevented from entering the discharge chamber 63 even in the inclined posture.

(3) Configuration of Developer Damping Portion FIG. 5 is an exploded perspective view showing the configuration of the developer damming portion 55, and FIG. 6A shows the opening 73 opened by the shutter 81. FIG. 6B is a cross-sectional view taken along the line CC shown in FIG. 6A, and FIG. 7A shows a state in which the opening 73 is closed by the shutter 81. FIG. 7B is a cross-sectional view taken along the line DD shown in FIG. 7A. In FIGS. 6 and 7, a part of the shutter 81 is shown in a transparent manner for easy understanding.

As shown in FIGS. 5 to 7, the developer damming portion 55 includes a shutter 81, a torsion coil spring 82, and a shutter drive actuator 83.
The shutter 81 includes a main body portion 811 for opening and closing the opening 73, a shaft portion 812 erected on the front side surface of the main body portion 811 toward the front side of the apparatus, and a pin 813.
The shaft portion 812 includes a large-diameter portion 821, a small-diameter portion 822 provided on the front side of the apparatus with respect to the large-diameter portion 821, and a protrusion 814 provided on the outer peripheral surface of the small-diameter portion 822. The torsion coil spring 82 is fitted in the small diameter portion 822.

One end of the torsion coil spring 82 is engaged with a pin 813 provided on the main body portion 811 and the other end is engaged with the housing 50, and the main body portion 811 is directed in the direction indicated by the arrow E in FIG. The rotational force is always energized.
A protrusion 814 provided on the shaft portion 812 is connected to a shutter drive actuator (hereinafter referred to as “actuator”) 83 formed of a solenoid or the like, and the actuator 83 connects the main body portion 811 with an arrow through the protrusion 814. A driving force for rotating in the direction opposite to the direction indicated by E is applied.

When the actuator 83 operates, the shutter 81 rotates by a certain amount in the direction opposite to the direction indicated by the arrow E against the urging force of the torsion coil spring 82 by the driving force from the actuator 83, as shown in FIG. The opening 73 is opened by the shutter 81. The position of the shutter 81 is referred to as an open position.
On the other hand, when the actuator 83 is stopped, the driving force from the actuator 83 is no longer applied to the shutter 81, and the shutter 81 is rotated in the direction indicated by the arrow E by the biasing force of the torsion coil spring 82, as shown in FIG. As shown, the opening 73 is closed by the shutter 81. The position of the shutter 81 is called a closed position.

By switching between operation and stop of the actuator 83, the shutter 81 can be switched from the open position to the closed position and from the closed position to the open position.
When the shutter 81 is switched from the closed position to the open position, a flow path (branch path 102) to the discharge chamber 63 for the developer D conveyed by the supply screw 52 as shown by the dashed arrow in FIG. It is formed. As a result, most of the developer D is conveyed through the opening 71 to the stirring chamber 62 positioned obliquely below the supply chamber 61 as indicated by the solid arrow, and the remaining part of the developer D is opened in the opening 73. It passes through the discharge chamber 63 located obliquely below the supply chamber 61.

When the shutter 81 is returned from the open position to the closed position, the flow path to the discharge chamber 63 of the developer D conveyed by the supply screw 52 is blocked as shown in FIG. It is transferred to the stirring chamber 62 through the opening 71 and is not transferred to the discharge chamber 63.
Switching between the open position and the closed position of the shutter 81 is executed by the control unit 15.
(4) Configuration of Control Unit FIG. 8 is a block diagram showing the configuration of the control unit 15.

As shown in the figure, the control unit 15 includes a CPU 151, a ROM 152, a RAM 153, and a shutter opening / closing control unit 154 as main components, and each unit can exchange data with each other. .
The CPU 151 controls the operation of each unit such as the image reading unit 11, the image forming unit 12, and the feeding unit 13 based on a control program stored in the ROM 152, thereby realizing a smooth color image forming operation. Further, based on the detection signal from the density detection sensor 56 for each of the developing units 4Y to 4K, the current ratio of the carrier and the toner of the developer D accommodated in the developing units 4Y to 4K is determined in advance as a reference. Judge whether it is within the proper range. For each color, control is performed to replenish the developer for replenishment from the corresponding color hoppers 7Y to 7K to the corresponding developing unit so that the ratio between the carrier and the toner is out of the appropriate range if the ratio is out of the appropriate range. .

The RAM 153 serves as a work area for the CPU 151.
The shutter opening / closing control unit 154 performs opening / closing control by the shutter 81 according to the posture (horizontal posture or inclined posture) of the developing unit for each of the developing units 4Y to 4K.
(5) Processing Contents of Opening / Closing Control FIG. 9 is a flowchart showing processing contents of the opening / closing control for the developing unit 4Y.

  As shown in the figure, when the power of the copying machine 10 is turned on (step S1), a detection signal of the developing unit inclination detection sensor 57 is acquired (step S2). When the power is turned on, the shutter 81 is returned to the closed position when the power is turned off last time (step S9 described later), and it is assumed that the shutter 81 is located at the closed position. Here, the power off may be, for example, a case where the power plug of the copying machine 10 is disconnected from a commercial power outlet or a case where the main switch of the copying machine 10 is turned off.

Then, it is determined whether or not the inclination of the developing unit 4Y is less than a predetermined amount (step S3).
Here, when the developing unit 4Y is inclined at an angle larger than this, a large amount of the developer D accommodated in the supply chamber 61 moves so as to be offset in the discharge chamber 63 by gravity, and the discharge port 59 This is an amount corresponding to an angle at which the total amount of the developer D is assumed to be reduced to such an extent that the development fading occurs, and is obtained in advance through experiments or the like, and the information is stored in the ROM 152 or the like.

When it is determined that the inclination of the developing unit 4Y is less than a predetermined amount, that is, in a horizontal posture, or within a range where development blurring does not occur (“YES” in step S3), the shutter 81 is moved. Move to the open position (step S4). The shutter 81 is moved to the open position by driving the actuator 83.
It is determined whether or not the power is off (step S7).

If it is determined that the power is not turned off ("NO" in step S7). Return to step S2.
If the developing unit 4Y is in the horizontal posture, the processes in steps S2 to S4 and S7 are repeatedly executed. Therefore, while the horizontal posture is maintained, the shutter 81 is in the open position, and the developer D is transported through the circulation path 101 and the branch path 102, and a part of the developer D in the supply chamber 61. Is conveyed to the discharge chamber 63 through the opening 73, and when the developer D conveyed in the discharge chamber 63 passes through the discharge port 59, a part of the developer D is discharged to the outside, and the discharge port 59 is not discharged. The remaining developer D that has passed through the position of the developer D is conveyed from the discharge chamber 63 to the stirring chamber 62 through the opening 74 and continues to be circulated.

  For example, when the developing unit 4Y is in an inclined position because the installation location of the copying machine 10 is temporarily moved by the user, or when the copying machine 10 is installed in a ship and is shaken by ocean waves, When it is determined that the inclination amount of the developing unit 4Y is equal to or greater than a predetermined amount when the horizontal posture and the inclined posture are alternately changed from the horizontal posture to the inclined posture ("NO" in step S3), At that time, it is determined whether or not the shutter 81 is in the open position (step S5).

Whether the shutter 81 is in the open position is determined by determining that the shutter 83 is in the open position when the actuator 83 is driven, and the closed position when the actuator 83 is stopped. Alternatively, for example, a position sensor may be used to directly detect the position of the shutter 81.
If it is determined that the shutter 81 is in the open position (“YES” in step S5), the shutter 81 is moved to the closed position (step S6), and the process proceeds to step S7.

On the other hand, if the shutter 81 is not in the open position, that is, if it is in the closed position (“NO” in step S5), the process proceeds to step S7 as it is. The movement of the shutter 81 to the closed position is performed by stopping the driving of the actuator 83.
If the developing unit 4Y is tilted, the processes of steps S2, S3, S5, and S7 are repeatedly executed. Therefore, while in the inclined posture, the shutter 81 is located at the closed position, the branch path 102 is blocked at the entrance thereof, and the developer D is transported only to the circulation path 101, so that the inside of the supply chamber 61 is The developer D is not transported to the discharge chamber 63.

As a result, the developer D, which should originally exist in the supply chamber 61 due to the inclination, is prevented from moving into the discharge chamber 63 due to gravity and being discharged from the discharge port 59, and the development in the discharge chamber 63 is prevented. Since the agent D does not exist in a biased manner, the developer D in the developing unit 4Y is not suddenly reduced even when the inclined posture is returned to the horizontal posture.
When the developing unit 4Y is returned from the inclined posture to the horizontal posture (“YES” in step S3), the shutter 81 is moved to the open position (step S4), and the developer D in the supply chamber 61 is transported to the discharge chamber 63. Is resumed.

If it is determined that the power is off (“YES” in step S7), it is determined whether or not the shutter 81 is in the closed position (step S8).
If it is determined that the shutter 81 is not in the closed position but in the open position (“NO” in step S8), the shutter 81 is moved to the closed position (step S9), and then the power is turned off (step S10). End control. On the other hand, when it is determined that the shutter 81 is in the closed position (“YES” in step S8), the power is turned off as it is (step S10), and the control ends. When the power is turned off, the actuator 83 remains stopped, and the urging force of the torsion coil spring 82 acts on the shutter 81. Therefore, the shutter 81 is in the closed position while the power is turned off. Positioned and the closed state of the opening 73 is maintained. This prevents the developer D from flowing into the discharge chamber 63 even when the developing unit 4Y is in an inclined posture while the power is off.

In the above description, the contents of the opening / closing control for the developing unit 4Y have been described, but the same control is performed for the other developing units 4M to 4C.
As described above, in the present embodiment, when the developing unit is inclined, the development that prevents the developer D from flowing into the discharge chamber 63, that is, flows through the branch path 102 toward the discharge port 59. The operation of damming the agent D is executed.

Accordingly, since the discharge chamber 63 (branch path 102) is positioned lower than that in the horizontal posture due to the inclined posture, the developer D in the supply chamber 61 flows into the discharge chamber 63 due to gravity and is discharged into the discharge port. Thus, it is possible to prevent development fading from occurring due to a rapid decrease in the developer D in the developing unit due to a change in posture.
In the above description, the shutter 81 is moved to the closed position when the power is turned off. However, the present invention is not limited to this. For example, after the power is turned on again after being moved to the open position, the developing unit may be inclined. If detected, the shutter 81 may be moved to a closed position.

<Embodiment 2>
In the above embodiment, the shutter is controlled to be opened and closed in order to prevent the developer D from flowing into the discharge chamber 63 when the developing unit is in the inclined posture. Instead of the opening / closing control, a dam (dam) for damming the developer D flowing through the branch path is provided, which is different from the first embodiment. Hereinafter, in order to avoid duplication of description, the description of the same contents as those of Embodiment 1 is omitted, and the same components are denoted by the same reference numerals.

(1) Configuration of Developing Unit FIG. 10 is a plan view showing a device front side portion 505 of the developing unit 4Y according to the second embodiment, and FIG. 11 is a horizontal plane view of the device front side portion 505 of the developing unit 4Y. And FIG. 12 is a perspective view of the supply screw 52 viewed from the direction of the arrow F shown in FIG. 11. 13 is a perspective view showing a state where the supply screw 52 shown in FIG. 12 is removed, FIG. 14 is an enlarged perspective view showing the configuration of the dam 200, and FIG. 15 is a GG shown in FIG. It is arrow sectional drawing of the dam 200 in a line.

As shown in FIGS. 10 to 15, in the present embodiment, the supply screw 52 extends to the end portion on the front side of the apparatus, and in the housing 50, from the end portion on the front side of the apparatus of the supply screw 52 in the longitudinal direction of the apparatus. The part up to the opening 71 constitutes the discharge chamber 63, and the part from the opening 71 to the end on the rear side of the apparatus constitutes the supply chamber 61.
The supply screw 52 is provided with a spiral blade for transporting the developer D from the rear side of the apparatus toward the front side of the apparatus on the peripheral surface of the shaft portion 529, but the rear side of the discharge chamber 63 (developer transport) A reverse winding portion 541 having a reverse spiral direction is provided only at an end portion on the upstream side in the direction.

The developer D accommodated in the supply chamber 61 is conveyed from the rear side of the apparatus toward the front side of the apparatus by the supply screw 52, and most of the conveyed developer D passes through the opening 71 and enters the stirring chamber 62. It is conveyed and a part passes through the reverse winding part 541 and is conveyed through the discharge chamber 63.
A discharge port 59 is provided in the middle of the discharge chamber 63, and a part of the developer D transported through the discharge chamber 63 is discharged from the discharge port 59, and the remaining developer D that has not been discharged. It is conveyed to the stirring chamber 62 through the opening 74 on the front side of the apparatus. A flow path 101 shown in FIG. 11 corresponds to a circulation path, and a flow path 102 corresponds to a branch path 102.

As shown in FIG. 11, the dam 200 is located in the discharge chamber 63 at the front side of the apparatus (downstream side in the developer transport direction) from the reverse winding portion 541 of the supply screw 52 and the rear side of the apparatus (developer transport) from the discharge port 59. And provided with a rotating body 201 and a fixing member 202.
As shown in FIG. 14, the rotating body 201 is a circular plate-like member that is provided on the peripheral surface of the shaft portion 529 of the supply screw 52 and is concentric with the shaft portion 529 and rotates integrally. It can be made of resin. Note that the configuration is not limited to a configuration in which the shaft portion 529 is a separate member. For example, the shaft portion 529 may be configured to also serve as the rotating body 201 by increasing the diameter of the shaft portion 529.

The fixing member 202 is an arc-shaped member that is partially cut out and has a C-shape when viewed in the axial direction, and the inner peripheral surface thereof is the outer peripheral surface of the rotating body 201 with the cut-out portion positioned above. It is provided on the inner surface of the discharge chamber 63 of the housing 50 so as to be in sliding contact with the housing.
The fixing member 202 is made of an elastic body such as urethane foam, but the material is not limited to this, and may be made of resin or metal, for example. Further, the fixing member 202 is not limited to being attached to the housing 50 as a separate member from the housing 50. For example, when the housing 50 is made of resin, it may be formed by integral molding with the housing 50.

As shown in FIG. 15, both ends 211 and 212 in the circumferential direction of the fixing member 202 are located above a horizontal plane 299 passing through the axis of the shaft portion 529, and the discharge chamber 63 is fixed to the inner peripheral surface 630. Except for the space 210 surrounded by the circumferential ends 211 and 212 of the member 202 and the outer peripheral surface of the rotator 201, the member 202 is blocked by a weir composed of the rotator 201 and the fixed member 202.
Accordingly, the flow of the developer D that has rotated the supply screw 52 and passed through the reverse winding portion 541 into the discharge chamber 63 is blocked by the dam 200, but the blocked developer D is from the dam 200. Is stored at the upstream side in the transport direction, and the total amount of developer D is increased by supplying the replenishment developer to the developing unit 4Y by the trickle developing method, or when the posture of the developing unit 4Y is changed from the horizontal posture to the inclined posture. Due to the deviation of the developer D due to gravity, the storage amount increases, and further increases after the agent surface Da of the developer D reaches both ends 211, 212 (upper limit level) of the fixing member 202 as shown in FIG. When the height of the agent surface Da is about to be higher than the two ends 211 and 212, the increased amount of the developer D overflows over the dam 200.

The developer D overflowing beyond the dam 200 is transported toward the discharge port 59 by receiving the transport force of the supply screw 52 by the spiral blade on the downstream side of the rotating body 201.
The storage of the developer D by the dam 200 is performed in the same manner whether the developing unit 4Y is in a horizontal posture or in an inclined posture, and the developer surface Da of the developer D is higher than the height of the dam 200. Therefore, if the dam 200 is low, the storage amount is small (the total amount of the developer D is small), and the storage amount increases (the total amount of the developer D is large). When the total amount of the developer D in the developing unit 4Y varies depending on the developing method, the variation range is determined by the height of the dam 200.

(2) Variation range of total amount of developer D FIG. 17 is a diagram showing an experimental example in which the variation range of the total amount of developer D due to the inclination of the developing unit 4Y changes, and FIG. An example according to the embodiment, (b) shows a comparative example. Here, a comparative example is a structure which does not provide the dam 200, and the thing of the same structure as this Embodiment is used except this.

In the experiment, the entire amount of the developer D that changes by the trickle developing method when the developing unit 4Y is maintained in a horizontal posture (swing angle = 0 °) and normal image formation is continuously performed is the maximum. The number of grams at the minimum and the minimum was measured, and the range from the measured minimum value to the maximum value was set as a reference developer amount fluctuation range 250 (260 in the comparative example).
Then, when the developing unit 4Y is repeatedly swung for 30 seconds as one cycle so that the front end and the rear end of the apparatus alternately rise and fall with the center in the longitudinal direction of the apparatus as a fulcrum with respect to the horizontal posture, The amount of change in the developer amount with respect to the reference developer amount fluctuation range is changed to 7.5 ° when the rocking (tilt) angle is 3.5 ° and 5 °. In each case, the maximum and minimum of the total amount of developer D were measured under the same conditions as when the reference developer amount fluctuation range was obtained.

Looking at the experimental results, the minimum value of the developer amount fluctuation range in both the example and the comparative example decreases as the swing angle increases. This is because every time the discharge chamber 63 is positioned below the horizontal posture due to rocking, the larger the rocking angle, the greater the amount of developer exceeding the dam 200 due to gravity, and the smaller the developer amount. is there.
On the other hand, the maximum value of the developer amount variation range is the same regardless of the swing angle. This is because the height of the dam 200 is constant regardless of the swing angle, and the maximum value of the amount of developer D stored by the dam 200 does not change regardless of the horizontal posture or the inclined posture.

Note that a frame indicated by a broken line in FIG. 17 indicates a range (appropriate maintenance range) of the entire amount of developer D that can maintain an appropriate image (appropriate image level) by development.
Here, the minimum value of the appropriate maintenance range is a lower limit value of the developer amount that is assumed to cause no development fading even if the developer amount is reduced to this value, and particularly in the inclined posture. In this case, since the amount of developer at the upper end of the developing unit 4Y in the front-rear direction of the apparatus becomes insufficient, development fading is likely to occur.

In the figure, the inclination angle is 0 °, and the minimum value of the appropriate image level is about 180 grams, but when the inclination angle becomes 5 °, it increases to about 200 grams, and when the inclination angle becomes 7.5 °, it increases to about 260 grams. An example is shown.
On the other hand, if the maximum value of the appropriate maintenance range is up to this value even if the amount of developer increases, the rotational torque of the rotating body material such as the developing roller 51, the supply screw 52, and the stirring screw 53 increases. The load applied to the rotating drive motor, drive system, etc. is the upper limit of the amount of developer that is assumed not to cause a fluctuation in the rotation speed that should be constant and hinder development. Since the maximum value of the proper maintenance range is caused by the magnitude of the rotational torque of each screw, it is the same value regardless of the magnitude of the swing angle.

  In the embodiment shown in FIG. 17A, the developer amount fluctuation ranges 251 and 252 are within the proper maintenance range when the swing angle is 5 ° or less, and this causes the developing unit 4Y to swing. It can also be seen that if the swing angle is 5 ° or less, an appropriate image level can be maintained. Note that when the swing angle is 7.5 °, the developer amount fluctuation range 253 protrudes from the appropriate maintenance range on the minimum value side, and if it is tilted to 7.5 °, the image is blurred even in the configuration of the embodiment. May occur.

  On the other hand, in the comparative example shown in FIG. 17B, the developer amount fluctuation range 260 when the reference rocking angle is 0 ° is within the proper maintenance range, but is 3.5 °, 5 °. , 7.5 °, the developer amount fluctuation range 261, 262, 263 has a lower limit value that protrudes from the lower limit value of the proper maintenance range. It can be seen that the image quality by development can be more stable against the rocking of the developing portion.

  In the comparative example of FIG. 17B, the minimum value of the developer amount fluctuation range is smaller than that in the example. This is because the comparative example does not include the dam 200 in the discharge chamber 63. When the developing unit is inclined as described above, the developer D freely flows through the gap between the spiral blade of the discharge screw 54 and the bottom surface 502 of the discharge chamber 63 and is discharged from the discharge port 59. This is because the amount of discharge increases as the tilt angle increases.

In addition, the maximum value of the developer amount fluctuation range is slightly smaller than that in the embodiment, but this is because the discharge chamber 63 is not provided with the dam 200 and only the reverse winding portion 541 tries to enter the discharge chamber 63. This is because the amount of developer discharged is larger than that of the embodiment in which the flow of the developer D is blocked by the dam 200, and the maximum value is lowered accordingly.
As described above, the developing unit according to the second embodiment is provided with the dam 200 for damming the developer D that is going to the discharge port 59 in the discharge chamber 63 (branch path 102). Even in the inclined posture, at least the amount of developer that can be dammed by the dam 200 can be prevented from being discharged from the discharge port 59. Compared with the configuration in which the dam is not provided, the developer in the developing unit The sudden decrease can be reduced.

Further, it is only necessary to add the dam 200 to the existing configuration, and the shutter moving mechanism is unnecessary as in the first embodiment, so that the space can be saved correspondingly.
In the above description, the area corresponding to 3/4 (= 75%) including the lowermost part around the shaft core (axis) of the shaft portion 529 of the supply screw 52 in one round on the outer peripheral surface of the rotating body 201. The inner peripheral surface of the fixing member 202 is in sliding contact (the periphery of the rotating body 201 is surrounded by the fixing member 202 only in an area corresponding to 3/4 of one rotation). The circumferential length of the slidable area is not limited to this.

  It only has to function as a weir for the developer D, and the length (weir height) suitable for the configuration is determined according to the apparatus configuration from the storage amount of the developer D when the weir is horizontal and inclined. However, for example, it is desirable that it is less than one circle and 2/5 (= 40%) or more including the lowermost part of one circle. This is because if the amount is less than 40%, the weir becomes too low, and the function as the weir is often difficult to work.

In the case of the range of less than 50% and 40% or more of the circumference, the circumferential ends 211 and 212 are more than the horizontal plane 299 in order to balance the upper limit levels depending on the height positions of the circumferential ends 211 and 212 of the fixing member 202. It is preferable that the positional relationship is such that
In the above description, the dam 200 is configured by the rotating body 201 and the fixed member 202, but the present invention is not limited thereto. A structure having a rotating portion and a fixed portion surrounding the periphery of the rotating portion with less than one round, that is, a circular rotating portion that is provided on the discharge (conveyance) screw 54 over the entire rotation direction and rotates together with the discharge screw 54. And an arcuate fixing portion that slidably contacts the circumferential surface of a portion of the circular rotating portion that extends along the circumferential direction on the inner surface of the discharge chamber 63 and rotates and includes at least the lowermost portion. It can be set as the structure provided.

Furthermore, in the above-described embodiment, the dam 200 is composed of the rotating body 201 and the fixed member 202. However, the present invention is not limited to this, and development is performed by the dam until the developer surface of the developer D exceeds the dam, both in a horizontal posture and an inclined posture. It is sufficient that the developer D is accumulated on the upstream side in the developer conveying direction and the developer exceeding the dam is discharged from the discharge port when the developer D exceeds the dam due to excess.
For example, without providing the rotating body 201, as a dam, in the middle of the conveyance path of the cylindrical discharge chamber, as shown in FIG. A D-shaped fixing plate 301 having a through-hole 302 is provided at the center, and the shaft portion 529 of the supply screw 52 is inserted into the through-hole 302 of the fixing plate 301 without a gap, so that the shaft portion 529 of the supply screw 52 is inserted. The developer D in the discharge chamber 63 can be conveyed by the rotation. Note that a seal or the like may be interposed to eliminate a gap between the shaft portion 529 and the inner peripheral surface of the through hole 302. In the figure, the reverse winding portion is not provided, but a reverse winding portion may be provided.

Moreover, as shown in FIG.18 (b), it can also be set as the structure which provides the fixed plate 303 whose height is lower than the fixed plate 301 shown to Fig.18 (a).
When the configuration shown in FIG. 18 is adopted, the rotating body 201 is not provided, so that the cross-sectional shape of the inner peripheral surface of the discharge chamber 63 (branch path 102) is not limited to a cylindrical shape, for example, a rectangular tube shape. good. In the case of a rectangular tube shape, the outer shape of the fixed plate 301 is formed in a square shape corresponding to the rectangular tube shape. The fixed plate 301 or the like is not limited to a plate shape, and may have a shape having a certain thickness.

  The present invention is not limited to the developing device, and may be a method of damming the developer passing through the branch path toward the discharge port in the inclined posture. The method may be a program executed by a computer. The program according to the present invention can be read by a computer such as a magnetic disk such as a magnetic tape or a flexible disk, an optical recording medium such as a DVD-ROM, DVD-RAM, CD-ROM, CD-R, MO, or PD. It can be recorded on various recording media, and may be produced, transferred, etc. in the form of the recording medium, or in the form of a program, including wired and wireless networks including the Internet, broadcasting, telecommunications lines, In some cases, the data is transmitted and supplied via satellite communication or the like.

<Modification>
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In Embodiment 1 described above, as a damming member for opening and closing the inlet of the discharge chamber 63 (branch path 102) when in an inclined posture, the inlet is closed (dammed) first. The configuration example in which the shutter 81 that can be moved between the position and the second position that is in the open state (releasing the blocking) is provided as an opening and closing member that opens and closes the flow path of the developer D has been described. Not limited. Any configuration can be used as long as it is possible to switch between damming and releasing the developer D going to the discharge port 59 in the branch path 102.

  For example, instead of a shutter that moves between the first position and the second position, the diaphragm mechanism that is arranged in the middle of the entrance of the branch path 102 or the outlet 59 and that overlaps a plurality of diaphragm blades is opened and closed. It is also possible to adopt a configuration that is provided as a member and switches between a closed state (a state where the flow path is blocked) and an open state (a state where the flow path is opened) by a driving force such as an actuator. Similarly to the shutter 81, this diaphragm mechanism also applies a biasing force to a position at which the flow path is blocked by the biasing means such as a spring until the power is turned on next time when the power is turned off. It is preferable to apply and to be configured so that the cut-off state is maintained mechanically.

If the flow of the developer D can be blocked, for example, the movable weir is raised at the time of damming and the flow is cut off. It is also possible to adopt a configuration that allows flow.
Furthermore, the damming position of the developer D may be, for example, a position between the inlet and the discharge port 59 in the branch 102 regardless of the inlet of the branch 102.

  (2) In the second embodiment, the configuration example in which only the dam 200 is provided in the developing unit has been described. However, the present invention is not limited to this. For example, the inner circumferential surface of the discharge chamber 63 and the dam 200 are only inclined. It is also possible to provide a member that closes the space 210 existing between the two and closes the flow path of the developer D. As a member that closes the space 210, a movable shutter that moves to a position where the space 210 is closed when the horizontal posture is retracted to a position where the space 210 is opened and is inclined can be considered.

(3) In the above embodiment, an example in which the image forming apparatus according to the present invention is applied to a tandem type color copying machine has been described, but the present invention is not limited to this.
Regardless of color or monochrome image formation, the two-component developer containing the carrier and toner contained in the housing is circulated and conveyed, while the developer for replenishment is replenished in the housing and excessive development is performed. A part of the developer is discharged to the outside from the discharge port, and the developer being conveyed is supplied to a developer carrier such as a developing roller, and the photosensitive drum is developed by the developer carried on the developer carrier. The present invention can be applied to a developing device that develops a latent image formed on an image carrier such as the above, and an image forming apparatus including the developing device, such as a printer, a facsimile machine, and a multi function peripheral (MFP).

Needless to say, the shape, size, material, and the like of each member such as the shutter 81 and the dam 200 are not limited to those described above.
Furthermore, in the above-described embodiment, the branch path 102 that branches from the middle of the circulation path 101 and then merges with the circulation path 101 is provided separately from the circulation path 101, and the developer D conveyed through the circulation path 101 is provided. A configuration in which a part of the developer D conveyed is discharged to the outside from the discharge port 59 while a part of the developer D is conveyed by the branch path 102 and the developer D remaining without being discharged is conveyed and returned to the circulation path 101. Although an example has been described, the branch path is not limited to this.

Any branch path may be used as long as it is branched from a circulation path for circulating and conveying the developer and a part of the developer flowing from the circulation path is conveyed toward the discharge port 59. For example, a configuration may be employed in which a branch path branched from the middle of the circulation path 101 does not join the circulation path again. In the case of this configuration, all of the developer D conveyed through the branch path is discharged to the outside from the discharge port.
In the above description, the reverse winding portion 541 is provided on the supply screw 52. However, the present invention is not limited to this, and the reverse winding portion 541 may not be provided.

Further, the developer is transported using the supply screw 52 having a spiral blade, but the rotary transport member having a function of transporting the developer along the rotation axis direction is not limited to the one having the spiral blade. Other shapes may also be used.
Further, the two-component developer containing the carrier and the toner may be composed of the carrier and the toner, or may be an additive mixed with the carrier and the toner.

  The contents of the above embodiment and the above modification may be combined.

  The present invention can be widely applied to a developing device that develops a latent image formed on an image carrier such as a photosensitive drum with a developer and an image forming apparatus including the developing device.

1Y, 1M, 1C, 1K Photosensitive drum 4Y, 4M, 4C, 4K Developing unit 7Y, 7M, 7C, 7K Hopper 10 Copying machine 15 Control unit 50 Housing 51 Developing roller 52 Supply screw 53 Stirring screw 54 Discharge screw 55 Weiring Section 57 Developing section inclination detection sensor 59 Discharge port 71, 72, 73, 74 Open section 81 Shutter 83 Shutter drive actuator 101 Circulation path 102 Branch path 153 Shutter opening / closing control section 200 Weir 201 Rotating body 202 Fixed member 210 Space 211, 212 Fixed Both ends 301, 302 of the member in the circumferential direction Fixed plate 502 Bottom surface 529 Shaft portion D Developer

Claims (5)

In this system, the developer contained in the housing is circulated and conveyed, and a part of the excess developer is discharged from the discharge port to the outside while replenishing the developer for replenishment in the housing. A developer that supplies the developer to a developer carrier and develops the latent image formed on the image carrier of the image forming apparatus with the developer carried on the developer carrier,
A circulation path for circulating and conveying the developer;
A branch path for branching from the circulation path to convey a part of the developer flowing from the circulation path toward the discharge port;
A damming means for damming a developer that flows through the branch path toward the discharge port at a position between the inlet of the branch path and the discharge port;
A rotation conveying member that conveys the developer existing in the branch path along the rotation axis direction;
Equipped with a,
The damming means is
A dam provided at a position between the entrance of the branch path and the discharge port;
The developer is accumulated on the upstream side in the developer conveying direction of the dam until the developer surface of the developer exceeds the dam, and the developer exceeding the dam is discharged from the discharge port. Yes,
The branch path is composed of a cylindrical member,
The rotary conveying member is
The axial direction is arranged in the inner space of the cylindrical member so as to follow the developer conveying direction,
The discharge port is provided in the cylindrical member,
The dam is
A circular rotating portion that is provided over the rotation conveyance member and rotates around the rotation conveyance member; and
An arcuate fixing portion that extends along the circumferential direction on the inner surface of the cylindrical member, and that slidably contacts an outer circumferential surface of less than one circumference including at least a lowermost portion of the rotating circular rotating portion. ,
Developing apparatus is characterized in that it comprises. Wherein the fixing portion, the circumferential length of the sliding contact region on the outer peripheral surface of the rotating part, the developing device according to claim 1, wherein the at around less and 40% or more of the round. The circumferential length is less than 50% of the circumference;
The developing device according to claim 2 , wherein both ends of the fixing portion in the circumferential direction are located below a horizontal plane passing through an axis of the conveying screw. The branch path is
After branching from the circulation path, it is a flow path that joins the circulation path again.
An apparatus according to any one of claims 1 to 3, characterized in that the outlet in the middle of the flow path is provided. An image forming apparatus having a developing unit that develops a latent image on an image carrier with a developer,
Examples developing unit, an image forming apparatus comprising: a developing device according to any one of claims 1-4.

Images